Which phenomenon provides an entirely independent, geometric method for mapping the mass distribution, visible or dark, of a foreground galaxy?

Answer

Gravitational lensing.

Gravitational lensing occurs because mass warps spacetime, bending the path of light from a distant source, allowing mass distribution to be mapped geometrically, which is independent of kinematic measurements.

Which phenomenon provides an entirely independent, geometric method for mapping the mass distribution, visible or dark, of a foreground galaxy?
measurementgalaxyastronomymethodmass